Bomb sight



K. cLARK Jan. 25 1.949;

BOMB SIGHT 'iv sheets-sheet 1 Filed March 3l, 1944 L l M T INVENTOR. C

K. CLARK B OMB SIGHT Jan. 25, 1949.

Filed March 31, 1944 7 Sheets-Sheet 2 20w lo INVENTOR.

Jan. 25, E949. K. cLAK 2,459,919

BOMB SIGHT Filed March 3l, 1944 '7 Sheets-:Sheet 3 IN VEN TOR.

K. CLARK Jan. 25, 1949.

BOMB S IGHT 7 Sheets-Sheet 4 Filed March 3l. 1944 8 #fus "A INVENTOR.

7 Sheets-Sheet 5 K. CLARK BOMB SIGHT 12.9 IIB Jan. 25, 1949.

Filed March 31, 1944 Jan. 25, i949. K. CLARK 2,459,919

BOMB SIGHT Filed MarCh 3l, 1944 7 Sheets-Sheet 5 LINE B LINEA K'. CLARKBOMB SIGHT Jan. 25, 1949.

'7 Sheets-Sheet 7 Filed March 5l, 1944 i ai Patented Jan. 25, 1949 BOMBSIGHT Kendall Clark, Oakwood, Ohio, assignor to General MotorsCorporation, Dayton, Ohio, a corporation oi' Delaware Application March31, 1944, Serial No. 529,013

(ci. .t3-46.5)

13 claim. l

This invention relates to aeronautical apparatus and more particularlyto bombsights for low and medium altitude bombing.

The famous precision bombsights which are now used for high altitudebombing are not satisfactory for low altitude bombing. One of thereasons for this is that these high altitude bombsights use a telescopesight and when used at low altitudes the target on the ground flashes bybeneath the plane so rapidly that it is dimcult to follow it with such asight. Such precision bombsights are also very complicated, expensiveand diflicult to manufacture. In many situations it is of advantage touse low or medium altitude bombing rather than high altitude bombing.

It is therefore an object of my invention to provide a new and improvedbombsight for low and medium altitude bombing which is simple.inexpensive and readily manufactured.

It is another object of myinvention to provide a low and medium altitudebombsight which employs a collimating sight. A

It is another object of my invention to provide a simple, easilymanufactured bombsight which can be so accurately set and adjusted forthe effect of wind, the air friction characteristics of the bomb and theplane speed and direction, and which provides an accurate indication ofthe releasing point of the bomb.

It is another object of my invention to provide a bombsight whichincorporates a very simple calculating device making it possible toaccurately set the bombsight without reference to bombing tables ataltitudes less than 3,000 ft.

It is still another object of my invention to provide an improvedbombsight with improved and more simple mechanism for maintaining a truevertical reference as well as a more simple mechanism for setting intothe bombsight drift, cross trail and dropping angle.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings, wherein a preferred form of the present invention is clearlyshown.

In the drawings:

Fig. 1 is a diagrammatic illustration of the use of my improvedbombsight in a level bombing attack;

Fig, 2 is a perspective view of the upper portion of my bombsightshowing the dropping angle and cross trail knobs;

Fig. 3 is a fragmentary view showing the gearing arrangements for thedropping angle setting device;

Fig. 4 is a top sectional view of my improved bombsight set for a degreedropping angle and zero drift and cross trail;

Fig. 5 is a fragmentary sectional view similar to, Fig. 4 with thebombsight set at a 60 degree dropping angle, a 15 degree drift andsubstantially maximum cross-trail;

Fig 6 is a vertical sectional view taken substantially along the line8,-8 of Fig. 4;

Fig. 'I is a sectional view taken substantially along the line 'I-l ofFig. 6; u

Fig. 8 is a sectional view taken substantially along the line 8-8 ofFigs. 4 and 6; u

Fig. 9 is a fragmentary sectional view takenl The problem of bombingReferring now more particularly to Fig. l, there is showndiagrammatically my improved bombsight including the head 20 and thecollimator 22. The support ISI for the head and co1- limator is normallyheld in a fixedl position relative to the aircraft in which it isinstalled andin Fig. 1 corresponds to the heading of the aircraft whichis indicated by an arrow so marked. Beneath this arrow and parallel toit is an air speed arrow indicating the speed and heading of theaircraft. An arrow is also provided for the wind speed and the vectorsum of the air speed and wind speed arrows designates the true groundspeed and direction designated by the' arrow which completes the vectortriangle. This ground speed arrow indicates the track of the aircraftcarrying the bombsight, which is indicated by the line AB.

The bombsight is shown at the releasing point of the bomb with thesighting line through the bombsight at the time of the bomb releaseextending directly to the target T on the ground. The

point B represents the position of the aircraft at target T is directlybeneath the point C on the line GH and the point D 1S a 13011117011 theline AB of a perpendicular from the point C as well as the target T.

The angle EAT represents the dropping angle, usually expressed indegrees, while the angle FBT indicates the trail angle, usuallyexpressed in mills. The line BC represents the trail and the line CDrepresents the cross-trail which is equal f to the trail times the sineof the drift angle, while the line ET which equals the lines ADk and GCrepresents the range. The line TF which is equal to the lines DB and CHrepresents the range component of the trail which isk approximatelyequal to the trail under normal conditions, particularly of low altitudebombing. This is true kThe sighting device n Instead of employing atelescopic sighting device, `I employ a reflecting type collimator. As

shown best in Fig. 8, this collimator includes a barrel 24 having areticule glass 28 fastened to i it by the ring 28 and suitable gasketsand screws.

The reticule glass 26 is preferably frosted on the side nearest the lampwhile the opposite side is provided with a silvered surface over whichblack lacquer is applied. Inscribed on thisL black lacquered andsilvered surface are two vertical lines .040" apart and a horizontalline provided 4 which ride upon the ends of the central outer finishedsurface of the barrel 24-nwhich is provided with shoulders at the 'endsagainst which the ball bearings 58 ride. The ball bearings are supportedupon the stub shaft projecting from the ends of three squared shafts 80which are fastened by the screws 62 to the collimator support 84. Thiscollimator support 64 includes a removable cap member 66 at its bottomwhich is fastened by screws to the remaining portion of the collimatorsupport 84.

AToone end of the collimator support. there is fastened by four screws alamp housing 68 provided with a removable lamp supporting bracket fromthe lamp upon the reticule glass 26. Al-

though the lamp housing 88 is shown fastened directly to the collimatorsupport 64 this is done for the reason of minimizing the movement of theelectric wiring 14 which connects to the lamp 12. It is also possible toconnect the lamp housing 58 directly to the optical barrel 24. In such`a case the electrical cord must move with the rotation of the barrel 24.The kreticule 26 is illuminated by the double lament lamp 12 which mayhave its intensity varied by a rheostat 16 with a .020" gap betweenthevertical lines forming the reticule. The other end of the barrel 24 isprovided with a flange 30 to which is fastened a bracket 32 providedwith a clear sealing glass 34 for sealing the optical barrel 24. Thissealing glass is held in place by a ring 36 and the fastening screws 38which fasten the bracket 32 to the ange 30 of the optical barrel.

The bracket 32 carries a. mirror supporting bracket 40 provided with anaxial groove 42 upon its lower surface which receives a pair of guidepins 44 which project up from the supporting surface of the bracket 32.The mirror supporting bracket 40 may be moved in or out guided by thegroove 42 and the pins 44. It is locked in its adjusted position by thefastening screws 48 (see Fig. 4). The mirror supporting bracket 48 isprovided with a ring receiving a mirror 48 of crown glass with apolished spherical surface of 10%" radius on the one side. The sphericalsurface is chrome plated or chrome aluminumized to provide the sphericalreecting surface which will not tarnish readily. The mirror 48 is heldin r place in its ring by the retaining plate 58 which is fastened byscrews to the end of the mirror bracket 40.

Adjacent the mirror the mirror Abracket is provided with a rib 52extending at an angle of 45 degrees to the axis of the mirror. To thisrib 52 is fastened, by screws, a reflecting glass plate 54 of clearoptical glass which extends completely across the face of the mirror andseveral inches beyond the mirror. The portion beyond the mirror isprovided with a center line 56. This line is preferably scratched intothe glass and filled with luminous paint.

The barrel 24 is rotatably mounted upon three pairs of ball bearings 58which serve as rollers which is adjusted by the knob 18. A doublethrowswitch for energizing either of the filaments is provided on the casing|05 so that in the eventone filament burns out the second lament can bereadily switched on.

By this arrangement when the vertical and horizontal lines formingthereticule kon the reticule glass 26 are illuminated and the mirror 48 isadjusted so that its focal point is at the reticule, an illuminatedimage of the reticule will appear on the reflecting glass 54. Whenproperly adjusted this illuminated image of the reticule will appear asif it were substantially fixed on an object in the distance and willprovide a sighting line perpendicular to the axis of the mirror 48 andthe center line 56 on the reflecting glass 54. In order to improve thisfocusing arrangement I have provided within the optical barrel 24 acorrecting glass 82 which is supported on an arm 84 extending from thebracket 32. This is sealed within the optical system and a desiccanttablet 8B is provided within the sealed barrel to absorb all themoisture within this sealed enclosure. This prevents any moisture fromcondensing upon the clear glass 34 at the end of the barrel opposite thelight 12. The correcting glass 84 is a clear optical plate glass 1A"thick. This correcting glass, to obtain the eiect desired, must bepositioned at an angle of 45 degrees to the axis of the mirror 48 andtransverse to the reflecting glass 54.

The pendulum structure The collimator 20 forms the bottom of a pendulumstructure having a universal pivot. The colllrntator support E4 ispivotally mounted upon a pair of pivot pins 81 which, are xed in theforked lower end of the pendulum arm 88 to form the cross trail axis.The lower end of the pendulum arm 88 is also provided with a, yoke 90.The upper end of the pendulum arm 88 is provided on opposite sides withball bearings 92 which are mounted upon hollow pivot pins 94 .erenceline.

extending inwardly from the rectangular gimbal ring 90. These hollowpivot pins 86 are threaded into the ring 99 and are fastened in place bylock nuts. The rectangular gimbal ring 96 is also provided with a set ofball bearings 91 which are mounted upon a pair of hollow pivot pins 98which are threaded through a set of ribs which extend across a largeaperture |03 in the bottom of the casing of the head 20. These ballbearings 92 and 91 mounted upon the pivot pins 94 and 98, together withthe gimba] ring 96, form the universal or Hookes joint pivot for Thependulum is so balanced that it will hang downwardly giving its arm atendency to remain in a vertical position so as to form a vertical refInasmuch as the airplane carrying the bombsight is buffetted aroundconsiderably while in the air the pendulum will tend to swing violentlyand would not remain suiliciently still to do any sighting with it undermost conditions. In order to stop the swinging of the pendulum and yetallow it to adjust itself to the vertical reference line at all times Iprovide a damping dome bracket |01 which is fastened on top of thependulum. This bracket includes a mounting.

section fastened in top of the pendulum arm 98 by screws and a couple ofbowed arms extending around the trail arm |99 and guide 2|6 up to aspherical surfaced dome |09. 'I'he radius of the spherical surface isstruck from the pivot point of the pendulum.

Resting on the spherical surface of this dome |09 is a flanged plungerprovided with a rounded friction button ||3 of a hard felt or otherfibrous friction material in actual contact with the surface of the dome|09. A flat spring ||5 presses down on the retaining screw which holdsthe friction button ||3 in resilient contact with the top surface of thedome |09 to snub the movement of the pendulum. This flat spring I5 isfastened to a pivoted bracket ||1 connected by the pivot pin l I9 to thedamping mechanism case I 2| which is fastened by the screws |23 to thevertical rear Wall of the casing |05. 'I'he spring ||5 is tensioned by aknob |25 fastened to the splined upper end of the screw |21 which bearsupon the pivot mem-ber I1 and is threaded into the damping case |2|. Byturning the knob |25 the tension of the spring ||5 upon the plungerholding the friction button 3 on the dome |09 may be increased ordecreased to increase or decrease the damping effect of the dampingmechanism. When the flight is smooth, only a light spring tension needbe used, but when the flight is rough the knob |2| should be adjusted toincrease the tension of the spring I5.

The damping case |2| is provided with an arm |29 having an aperturewhich receives and serves as a vertical guide for the plunger To allowthe pendulum to maintain a vertical position regardless of the tiltingof the plane, means are provided for intermittently lifting the plungerso that the friction button ||3 is lifted oil?` of the dome at a rate ofabout 400 times a minute. This mechanism, called a stabilizer or dampingmechanism, includes a small high speed electric motor |3| (see Fig. 10)fastened to` the damping case |2|. This motor |3| is provided with apinion |33 meshing with the idler gear |35 fixed to the shaft of theidler pinion |31 which meshes with the final gear |39 provided upon theeccentric or cam shaft which carries the eccen tric or cam |4|. Theidler gear shaft and the cam shaft are supported in bearingsfprovided inthe damping mehanism case |2I. Covers |42 enclose the gearing so that itmay be packed in a suitable lubricant.

The eccentric or cam |4| is provided with a follower ring |43 engaging afollower pin |45 which extends through a bushing in the damp ingmechanism case |2| and contacts the connecting pin |41 of a bell cranklever |49. This lever |49 is split into two halves and is provided witha horizontal arm which extends upon opposite sides of the plunger ||Ibeneath its head. This horizontal arm has a plurality of projections forcontacting the underneath side of the head at diametrically oppositepoints. When the motor operates through the reduction gearing itoperates the cam or eccentric |4| to reciprocate the follower pin |45and the bell crank lever |49 to intermittently raise the plungeri Il tointermittently relieve the pendulum of its damper. This allows thependulum to intermittently move to its true vertical position betweenintermittent damping. By this arrangement the pendulum is effectivelystabilized, so that a steady sight is ollvtained even though it ismounted in an alrp ane.

Drift correction In order to make possible to correct for drift, thecasing |05 is rotatably mounted upon a support member I5I. (See Fig. 7.)The axis of rotation is vertical and extends through the center point ofthe gimbal ring 96. In this arrangement the casing |05 is provided witha depending circular ange |53 while the support member |5| is providedwith an upwardly extending circular flange |55, which is shaped topermit the reception of a substantially spherical dust shield |51fastened to the flange |59 provided upon the pendulum member 88. i Thisdust shield |51 keeps dust from getting into the casing |05. The flange|55 is provided with two diametrically opposite projections |6| withrecessed portions inbetween so that they may receive the diametricallyopposite projections |63 provided upon the flange |53.

By this arrangement in assembling, the casing |05 is placed upon thesupport member |5| so that the projections |63 pass through the recessprovided between the projections |6| and then when the flange |53 restsupon the member |5l, the casing 05 is given a quarter turn so as tocause the projections |63 to overlay the projections |6| to form aninterlocking arrangement of the bayonet-slot-type (see Fig. 6 andcompare with Fig. 8). This arrangement permits the casing |05, thependulum, together with the collimator at its lower end, to be rotatedwith respect to the support |5|.

The means for doing this includes a gear segment |65 provided upon aportion of the support member |5| which is in mesh with a worm |61 upona shaft |69. To prevent backlash, the gear |1| is held against a bearingprovided in the drift bearing member |68 for the shaft |69, by a spring|13 provided upon the opposite end of the second bearing |15. Where thebobsight is controlled by an automatic computer, the gear |1| will be inmesh with a pinion whose shaft is rotatably supported in the bearing|11. The connection to the computer will be made through the threadedopening |19. The drift may be set into the instrument by sightingthrough the reflecting glass 54 onto the ground and turning the driftshaft |89 by its knob |8| until the oblects passing beneath the planefollow exactly the `ine 56inscribed on the reecting glass 54.

However, in most cases the setting will be `:aken from the instrumentsof the airplane which will supply the drift angle. For this reason airift scale |83 is fastened to the casing |05 and an .ndicator |81 isfastened to the support member The indicator |81 will thereby directlyin- :iicate the amount of drift which is set into the `nstrument Thiswill make it possible to turn ;he collimator so that the pivot pins 81are di- `ectly in alignment with the ground track of the airplane. Theaxis of the pins 81 is designated 1s the cross trail axis in Fig. 1, andis parallel Lo the lines GH, AB and EF. The heading of ',he aircraft isat an angle to the cross trail axis which corresponds to the angle ofdrift of the Jlane. The case |05 is rotated with the penduum andcollimator so that all these parts, when The cross trail adjustment Itis not enough merely to correct for the drift Jut it is also necessaryto correct for the lateral novement of the bomb due to the effect ofwind. It should be observed that the sighting line AT s in the planeABFE. This plane ABFE is not Vertical but is tilted at an angle CTD fromthe Vertical. In order to tilt the collimator through in angle equal tothe angle CTD so that its iighting line falls within this tilted planeABFE, .he collimator is pivotally mounted on the cross '.rail axisprovided by the pins 81. To properly '.ilt the collimator upon its crosstrail axis there s fixed to the support member 5| a vertical rec-;angular support bar I 89 fixed at its lower end vithin a groove |9|provided in the upper face )f the support member |5|. A stud |93proiects downwardly from the bottom of the bar ',hrough an aperture inthe support |5| and the zar |89 is secured in place by a nut |95 at theower end of the stud |93. The bar |89 extends lpwardly through anarcuate slot |91 in the :ottom of the casing |05. At the top of the bar|89 a cross trail alignment slotted arm |99 is se- :urely fastened by ascrew and by brazing so ;hat it is rigid with the bar |89 as well as thesupport |5I. By this arrangement, the cross ',rail slotted arm |99 willremain stationary as ',he casing |05 is rotated to correct for drift.The amount of cross trail is proportional to the sine if the drift anglemultiplied by the trail. However, instead of using the cross traildirectly in ;his instrument, the cross trail angle CTD is used,

In order to automatically compute this factor, ;here is provided on oneface of the casing |05 a. trail knob and dial 202 which is graduated inmills from zero to 400, as shown in Fig. 2. Ihis trail dial is fastenedonto a shaft which Nithin the casing 05 carries a gear 204 which :nesheswith a pinion 206 fixed to a second gear 208 in mesh with a secondpinion 2|0 which is rotatably mounted in a support member 2I2 within thecasing |05. Pivoted by the pin 2|4 ;o the support 2|2 is the cross trailguide memaer 2|6 which is provided with bearings 2|8 supporting a screw220. This screw 220 is connected by a flexible shaft 222 to the pinion2I0. Ihe screw 220 is provided with a nut 224 having a. projection 226which extends downwardly ahrough a slot 228 in the cross trail guide 2|6as well as through a slot 230 in the cross trail arm |99.

A comparison of Figs`- 4 and 5 will illustrate the action of this crosstrail adjustment. When there is no drift, the cross trail guide 2|6 andthe cross trail arm |99 are superimposed as shown in Figs. 4 and 8. Whenthere is drift, the casing |05, the trail dial 202 and the pivot pin 2|4will turn relative to the cross trail arm |99 as shown in Fig. 5. Theangularity of the cross trail guide 2|6 will be determined by theposition of the projection 226 of the nut 224. This projection willdetermine the point of intersection of the slot 228 of the guide 2|6 andthe slot 230 of the cross trail arm |99. This point of intersectiontogether with the position of the pivot pin 2|4 determines theangularity of the cross trail guide.

The cross trail guide together with the gearing 204 to 210 and thethreading of the shaft 220 and the nut 224 are so proportioned that theguide 2|6 is moved to an angle proportional to the angle CTD or GEA inFig. 1 representing the angle of cross trail or angle of lateraldeflection of the bomb. In order to tilt the collimator 20 upon itssupporting pins 81 forming the cross trail axis an amount equal to thiscross trail angle CTD, I provide a wire drive (see Fig. 12) whichincludes a wire 234 fastened at one end by a screw to an ear formed atthe end of the guide member 2I6 adjacent the bearing 2|8. This wire 234is supported upon an inclined pulley 236 rotatably mounted upon theinclined surface of the block 238 (see Fig. 10). After passing 180degrees around the pulley 236, the wire 234 passes through one of thebushings 98 and then extends degrees around the pulley 239 which isrotatably mounted upon the shaft 240 iixed in the upper end of thependulum member 88. The pulley 239 as well as its companion pulley 242,immediately beside it, are positioned so that the top of their groovesis substantially tangent to the axis of the hollow pins 98.

The wire 234 continues on around a pulley 246 fixed to a helical gear248 and both are rotatably mounted upon a shaft 250 which is fastened tothe one side wall of the pendulum member 88 by a nut 252. Closetolerances must be maintained to prevent axial movement of the helicalgear 248 and yet permit the gear to rotate freely. The bottom of thegear 248 meshes with a helical gear segment 254 fastened to the top ofthe collimator support 64 by a pair of screws appearing in Fig. 8 justabove the shaft 68. The collimator support 64 is machined to asubstantially cylindrical shape with its center based on the pins 81 andthis surface fits closely the lower end of the pendulum member 88. Thegear segment 254 is lodged within a groove extending across thecollimator support 64 transverse to the pivots 81, and segments 256 areprovided on opposite sides of the gear segment within this groove topreserve the seal at the bottom of the pendulum member 88. An accessopening in the pendulum member 88 opposite the shaft 250 is providedwith a removable cover 258.

The wire 234 is fastened to the bottom of the pulley 246 by solder inorder to prevent slippage. After passing degrees around the pulley 246,the wire 234 extends upwardly to the opposite side of the pulley 239 andthence passes 90 degrees around the pulley 239 and extends through theother hollow pivot pin 98 to the pulley 260 which is likewise rotatablymounted upon an 15 angular block 282, The blocks 238 and 262 hold thepulleys 23B and 230 at such an angle and the pulleys 235 and 260 havesuch a diameter that their upper edges are substantially in alignmentwith the end of the cross trail guide 2|5 while their lower edgesaregsubstantially in alignment with the hollow pivot pins 90.

. The wire 234 after passing 180 degrees around the pulley 260 connectsto a tension coil spring 264 which in turn is connected by a link 266 tothe end of the cross trail guide ZIB adjacent the bearing 2|8. Thetension coil spring 264 keeps the wire 234 taut at all times. Anylateral movement of the end of the cross trail guide 2|6 will cause alateral movement of the wire 234 which will turn the pulley 246 and itsgear 248. The turning of the gear 240 will cause the gear segment 254and the collimator support 34 to be rotated upon the pins 81 so as totilt the collimator corresponding to the angle CTD in Fig. 1. This tiltsthe axis of the collimator 20 which is marked dropping angle axis inFig. 1 since it -serves as the axis of rotation of the collimator.

The dropping angle adjustment The remaining adjustment of the bombsightis the adjustment of the collimator to the sighting line AT in Fig. 1.To make this adjustment there is provided a dropping angle knob upon theend face of the casing |05. This dropping angle knob 30| is providedwith a skirt bearing ten graduations corresponding to 10 degrees andthese graduations cooperate with an index mark 303 provided upon atransparent dial cover 305 which is provided upon the end face of thecasing |05. The knob 30| is fastened onto the splined end of a threadedshaft 301 which is rotatably mounted in bearings provided in the ends ofthe casing |05. The rear end of the shaft 301 is provided with a gear309, the hub of which is held tightly against the end of an axiallyadjustable bearing member 3|| threaded into the rear wall of the casing|05 and adjustably locked in place by a lock nut 3I3. The means forholding the hub of the gear 309 against the end of the bearing bushing3|| is a compression coil spring 3|5 which extends between the outer endof the bearing bushing 3H and a disc 3|1 xed on the reduced projectingend 3|9 of the threaded dropping angle shaft 301. A removable cover 32|is provided for access to this adjusting device by which the bearingbushing 3|| may be adjusted axially to move the dropping angle shaft301y axially for adjusting purposes.

The dropping angle screw or threaded shaft 301 carries the droppingangle nut 323 provided with a tongue 325 which rides in a groove 321parallel to the shaft 301 in the bottom of the casing |05. This nut 323carries a wire connector 329 connecting to the wire 33| (see Fig. 12)which passes 180 degrees clockwise around the pulley 333 rotatablymounted on the bottom of the casing |05. This wire 33| then extendsthrough the aperture in the adjacent hollow pivot pin 98 and thence aquarter of a revolution clockwise around the idler pulley 242. From thispoint the wire 33| extends through .a slot 330 in the top of thecollimator support 64' and is received within a groove 335 extendingaround the barrel 24 of the collimato: 20. The barrel 24 is alsoprovided with a transverse groove receiving a grooved key block 331 andthe wire is lodged and soldered within the groove of the key block 331so that the wire 33| is keyed t0 the barrel 24 of the collimator 20.

l -10 As mentioned in the beginning 0i this description the barrel 24 isrotatably mounted upon its axis by means of the three pairs of ballbearings which are mounted upon the ends of the shafts 30. The wire 33|continues 180 degrees counterclockwise in the groove 330 around thebottom or the barrel 24 and thence extends upwardly through the slot 332to the idler pulley 242 continuing degrees clockwise around the upperhalf of the idler pulley 242 and thence horizontally to the pulley 339which is rotatably mounted on the bottom of the casing |05. The wire 33|continues 180 degrees clockwise around the pulley 333 and extends to atension coil spring 34| which is hooked to the end of the wire connector329 fastened to the nut 323. By this arrangement, when the droppingangle knob 30| is turned to rotate the dropping angle screw 301, the nut323 is moved axially along the screw to move the wire 33| so as torotate the barrel 24 of the collimator 20. It isnecessary that this bevery exact.

The trail values for setting the knob 202 as well as the dropping anglevalues for setting the dropping angle knob 30| may be obtained fromtables which are made up from experimental tests on the bombs. However,in order to make it poslible to use this bombsight without resorting tothe tables there is provided a simple calculator for determining thedropping angle. It is not necessary for an experienced bomber to resortto tables for determining the position of the trail dial 202 since atlow altitudes at which it is intended the dropping angle may be set bythe calculator. The trail is quite small and the cross trail which isaffected by the trail is also very small so that this factor need not beset accurately. Forexample, the trail may be set to 30 mills for thispurpose. vIf desired, however, a simple calculator for the trail similarto the calculator provided for dropping angle may be provided.

The dropping angle calculator To calculate the dropping angle, thesplined end of the dropping angle shaft 301 is provided with a smallgear 343 which meshes with a large gear 345 fastened by screws to therear face of the calculator dial 341. This calculator dial 341 isprovided with ten curved lines marked 1 to 10 consecutively andadditional curved lines numbered 12 to 30 in even numbers only. Thesecurved lines represent dropping angle values at various plane speeds foraltitudes above the target of to 3000 ft. These curved lines are groovesin the dial which are filled with a uorescent paint. The transparentdial cover 305 is provided with a speed scale, at the side of which arenumbers to 260 at intervals of 20. `This scale and these numbers are inthe form of grooves on the rear face of the transparent dial cover 305which are lled with uorescent paint.

By placing the curved line corresponding to the altitude of the planeabove the target so that it crosses the speed scale at the pointcorresponding to the speed of the plane in M. P. H., the dropping anglewill be properly calculated for thebomb for which the scale is designed.In Fig. 2, the dropping angle dial and calculator is shown set for anyof the following conditions: 140 M. P. H. at 300ft.; 163 M. P. H. at 400ft.; 184 M. P. H. at 500 ft.; 204 M. P. H. at `600 ft.; 216 M. P. H. at700 ft., etc. Intermediatevalues may be interpolated. However, inasmuchas the variation between the different bombs in the correct droppingangle at altitudes up to 3000 ft., amounts to an error of not more than8 ft. on the ground, it

is possible to make one dial for the average characteristic of thedifferent bombs to be used which will be reasonably accurate for suchelevations. If greater accuracy is desired, separate dials for eachdifferent bomb may be provided and the dials changed to correspond tothe type of bomb to be used.

In the center of the dial 34`| there is provided the dropping angle dial349 which is rotatable independently of the calculator dial 341 and itsgear 345, but upon the same axis. This dropping angle dial 349 is fixedto the large gear 35| which meshes with the splined end of the shaft301. This gearing is made in such a ratio that one turn of the knob 30|corresponds to 10 degrees which is the interval between theV figures onthe dial 349. The dial 349 is marked to 90 in intervals of 10 and isprovided with an index which in Fig. 2 is directly to the right of theindex l0 on the dial 349 and vtaken with the scale on the knob 30|, adropping angle setting of 71.6 degrees is indicated. This index adjacentthe index is provided in the form of a groove on the rear face of thetransparent dial cover 305 which is preferably filled with fluorescentpaint.

The mounting The supporting member |5| is fastened to a c-shapedmounting bracket 402 (see Fig. 6). This mounting bracket 402 isrotatably supported upon a bearing member 404 provided with a verticaltube- 406. This bearing member 404 and its tube 406 are rotatablymounted in a suitable socket provided for it in the plane. Fixed to thelower end of the mounting bracket 402 is a bearing member 408 providedwith an index member 4|0 which cooperates with a scale provided upon thesocket in the plane. The position of the mounting bracket 402 relativeto the airplane is adjusted by the worm 4|2 which meshes with a rackprovided with the socket on the plane. After adjustment, this worm 4|2may be locked in place. A second worm 4|4 is rotatably carried by themember 408 and is provided with a knob (not shown). This worm 4|4 mesheswith a gear segment 4|6 which is fixed to a lever 4|8 which may beconnected to the turn dial provided in' the pilots compartment toindicate the course for the plane to follow in its bombing run. By thisarrangement the support |5| can always be adjusted to its properposition with respect to the plane.

The support 402 also carries a removable pin 420 which may be movedupwardly to enter an aperture in the yoke 90 as shown in Figs. 6 and 8,to prevent the movement of the pendulum 80 when the bombsight is notbeing used. 'I'his pin is provided with a lock in the form of a bayonetslot arrangement, not shown, which makes it possible to hold it free ofthe yoke 90, when it is in its down or disengaged position. When thelock is released the pin 420 will be held up in the position shown inFigs, 6 and 8 by the spring 422. This prevents any swinging of thependulum 88 when the bombsight is not in use.

While the form of embodiment of the invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted, as may come within the scope of the claims whichfollow.

What is claimed is as follows:

l. A sight comprising a support, a pendulum, a universal mountingconnecting the pendulum and said support, a sighting device mounted upon12 the pendulum :below the universal mounting, said pendulum beingprovided with a substantially spherical surface above said universalmounting, and vibrating damping means intermittently engaging saidsurface for sn'ubbing vibrations of the pendulum.

2. A sight comprising a rst movable support provided with a horizontalpivot, means for keeping said pivot horizontal, means for rotating saidpivot in a horizontal plane, a movable mounting pivotally supported uponsaid pivot, a

sighting device rotatably supported by said movable mounting upon anaxis transverse to the.

axis of said pivot, a second support for movably supporting said firstsupport, and means responsive to the relative movement between saidiirst and second supports for tilting said movable mounting upon saidpivot.

3. A sight comprising a nrst mox vtble support provided with ahorizontal pivot, means for keeping said pivot horizontal, means forrotating said pivot in a horizontal plane, a movable mounting pivotallysupported upon said pivot, a sighting device rotatably supported by saidmovable mounting upon an axis transverse to the axis of said pivot, asecond support for movably supporting said first support and meansresponsive to the relative rotation between said second support and saidpivot for tilting said movable mounting upon said pivot.

4. A sight including a first support, a pendulum suspended from saidfirst support, a universal mounting connecting the pendulum to thesupport to provide a universal pivot for the support, an opticalsighting device mounted upon said pendulum beneath said pivot, a memberprovided with a spherically shaped surface above said pivot, a memberhaving a portion of its surface normally in engagement with saidspherical surface, one of said members being connected to the pendulumand the other to said first support, means for intermittently separatingsaid members to allow the pendulum to move.

5. A sight comprising a first support, a second support rotatablymounted on said support on a substantially vertical axis, a thirdsupport connected to the second support by a universal connectionnon-rotatable with respect to said second support on a substantiallyvertical axis and provided with means for keeping itself in a definiterelationship to gravity, a fourth support pivoted to the third supporthaving a pivoting axis in a plane transverse to the pull of gravity, afifth support pivoted to the fourth support on an axis parallel to saidtransverse plane perpendicular to the pivoting axis of the pivotconnecting the third and fourth supports, a sighting means pro- Avidinga line of sight fixed to said fifth support,

and means for rotating the second support relative to the rst supportand for pivoting the fourth support relative to the third and the fifthsupport relative to the fourth to set the sighting means and the line ofsight to the desired position relative to the rst support.

6. A sight comprising a support, a member rotatably mounted upon saidsupport on the nominal vertical axis of said support, a pendulum, auniversal connection connecting said member and said pendulum, saidpendulum being provided with a pivot means in a plane perpendicular toits natural vertical axis and a mounting connected to and movable uponthe pivot means, said mounting being provided with a rotatable meanshaving an axis of rotation perpendicular to the axis of said pivot meansand a sighting device aesaois nection with said rst support and a secondthe second support and pivoting said lever thereby, and means responsiveto the relative movement between said first support and a portion ofsaid lever for moving said movable mounting.

3. A sight comprising a rst rotatable support provided with a horizontalpivot and means for keeping said pivot horizontal, a second support forrotatably supporting said iirst support, a movable mounting pivotallysupported on said pivot, said movable mounting being provided with abearing having an axis transverse to the axis o said pivot, a sightingdevice rotatably supported by said bearing, a lever provided with afirst pivotal connection with said ilrst support and a second pivotalconnection with said second support, means for moving said ilrst andsecond pivotal connections toward and away from each other, means forrotating said rst support relative to the second support and pivotingsaid lever thereby, means responsive to the relative movement betweensaid ilrst support and a portion of said lever for moving said movablemounting. and means for rotating said sighting device upon said bearing.

9. A sight including a mounting, a light source, a reticule illuminatedby the light source and supported by said mounting, a collimating meanssupported by said mounting for collimating the light rays emanating fromthe reticule, a trans-- parent reector plate upon said mountingpositioned in the path oi but at an angle to the collimated light raysso that the collimatcd rays are reflected by the plate to establish theimage oi the reticule and thereby a line oi sight, means for rotatablysupporting said mounting upon a second axis substantially parallel tothe axis of the collimating means, a second means for pivotallysupporting the iirst means upon a third axis at right angles to thesecond axis, a third means for rotatably supporting said second meansupon a fourth ams at right angles to the third axis. l

10. A sight including a mounting, a light source, a reticule illuminatedby the light source and supported by said mounting, a collimating meanssupported by said mounting for collimating the light rays emanating fromthe reticule, a transparent reiiector plate upon said mountingpositioned in the path of but at an angle to the co 2' ze light rays sothat the collimated rays are reected by the plate to establish the imageof the retioule and thereby a line of sight, means for rotatablyvsupporting said mounting upon a second axis substantially parallel tothe axis of the collimating means, a second means for pivotallysupporting the tiret means upon a third right anales to the second axis,a third l for rotatably supporting said second to the support, asighting device mounted ori saidpendulum but movably mounted relativemeansupon a fourth axis at right angles to the third axis, a universalconnection'between said second and third means and a stabilizing meansfor stabilizing said second means.

l1. A sight including a support, a pendulum, a universal connectionconnecting the pendulum thereto,v a pulley rotatably mounted upon saidpendulum ,having-,a point on the path of its rim substantiallycoinciding with the pivot point of l the pendulum, a manipulating meansmounted upon said support, and a thread extending from said manipulatingmeans over a portion of the rim of said pulley to said sighting devicefor moving the sighting device relative to the pendulum.

12. A sight including a support, a pendulum, a universal connectionconnecting the pendulum to the support, a sighting device movablymounted on said pendulum relative to two difierent axes, two pulleysrotatably mounted on said pendulum each having a point on the path ofits rim substantially coinciding with the pivot point of said'universalconnection, two manipulating means mounted upon said support, and athread extending from each of said manipulating means over a portion ofthe'rim of one of the pulleys to said sighting device for moving thesighting device upon the two different axes.

13. A sight comprising a rst rotatable support, a second support, forrotatably supporting the rst support, a movable mounting movablysupported on said first support, said movable mounting beingprovidedwith a sighting device, a lever member provided with a firstpivotal connection with one of said supports, a second memberxed to theother support, one of said members being provided with an elongatedslot, the other of said members being provided with a screw and a nutthreaded upon said screw, said nut having means extending into said slotto form a second pivotal connection, means for rotating the screw totraverse the nutthereon to move the pivotal connections toward or awayfrom each other, means for rotating the first support relative to thesecond support and pivoting the lever thereby, and means responsive tothe pivoting of said lever for moving said mounting relative to saidilrst support.

mDALL CLARK..

REFERENCES CITED The following references are oi record Ain the ille ofthis patent:

